Basic Gastrin (BG) the major component of circulating serum gastrin in man has been isolated, free of gastrins I and II, from porcine antral mucosa and preliminary testing of its biologic activity accomplished. The isolation of additional quantities and further characterization of the biologic properties of BG will be performed and compared with heptadecapeptide gastrin (HLG). Immunoreactively identical doses of BG and HLG are administered to gastric fistula dogs and volume and acid content of gastric output measured, as well as time to onset, time to peak and duration of action. Using radioimmunoassay serum levels will be correlated with acid output. Metabolic clearance rates will be determined for BG and HLG during infusion. Serum samples will be subjected to starch gel electrophoresis and BG and HLG components of circulating gastrin measured, as an attempt to determine if in vivo conversion of BG to HLG can be demonstrated.